Gas turbine power plant with closed gas circuit

ABSTRACT

Disclosed is a power plant having a nuclear reactor as a heat source and turbine assemblies comprising turbine, compressor and heat exchanger elements. The nuclear reactor is encased within a thermal barrier which is encased within a liner so as to form a free space between the thermal barrier and the liner. The free space is in communication with a cooling gas source, and the interior of the thermal barrier is in communication with a gas source. 
     Also disclosed is a method of cooling a nuclear reactor plant by passing a cooling gas into the free space between the liner and the barrier which is then passed to a recuperator after which it is passed within the thermal barrier surrounding the reactor.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a gas turbine power plant having a closed gascircuit in which a nuclear reactor acts as a heat source. At least onegas turbine assembly is provided including compressors, and heatexchangers. The devices comprising the same plant are arranged within areactor pressure vessel, whereby the nuclear reactor, surrounded by athermal barrier, is installed within a reactor cavity, coated by a linerand a gas circulation circuit for the power plant working gas andcooling gas communicating with the component parts of the plant.

Such a plant has the advantage that only the produced mechanical orelectrical power and cooling water, which has not come into contact withthe contaminated gas, need be led out of the reactor pressure vessel.The area outside of the reactor pressure vessel or tank is thusvirtually protected from the contaminated gas and the internal volume isoptimally utilized. Special connecting elements between the single plantparts carrying active gas are avoided by using integrated construction,which very favorably improves the construction and the operation of hightemperature reactors. Such a turbine power plant has, for example, beendescribed in German Offenlegungsschriften Nos. 24 04 843 and 24 54 451,and in respectively corresponding U.S. Pat. Nos. 3,998,057 and4,025,387, the disclosures of which are herein incorporated byreference.

2. Description of the Prior Art

It is also known to provide the reactor pressure vessel of such plantswith a steel plate liner to effect the sealing. The sealing liner isequipped on its inner surface with thermal insulation to protect theconcrete or cast metal wall of the reactor pressure vessel from the hightemperatures of the gases. At the same time, a cooling system isarranged on the outside of the sealing liner (on the side of thepressure vessel wall) through which water flows to protect the linerfrom too high a thermal load. With this arrangement, the insulatinglayer lying inside is penetrated by the coolant, while the sealing linerremains cold (cold liner). This construction type has the disadvantagethat the original sealing liner is covered by thermal insulation lyinginside, and thus the sealing liner is not accessible to inspection. Inorder to overcome this disadvantage, solutions have been proposed inwhich the sealing liner is directly exposed to the hot reactor coolingmedium, and the thermal insulation is arranged between the liner and thewall of the reactor pressure vessel.

German Offenlegungsschrift No. 22 36 026 describes a "hot liner" whichis manufactured of high heat-resistant material and, whereby its thermalinsulation layer, located between the liner and the prestressed concretecasing, is tightly adjacent to concrete casing. A cooling system isprovided in the area of the thermal insulation layer which decreases thetemperature to an acceptable level with respect to the prestressedconcrete.

German Offenlegungsschrift No. 23 58 142 discloses a further thermalinsulating system having a "hot liner" in which, in addition to a firstuncooled liner forming a tight metal skin, there is provided a secondliner which serves as a casing for the prestressed concrete and hascooling tubes along its outside. Thermal insulation is arranged betweenboth liners.

Further, German Offenlegungsschrift No. 23 42 262 illustrates a coolingsystem for the prestressed concrete vessel of a gas cooled nuclearreactor made up of at least two protective liner coverings, lying insideone another, with tubes welded to the latter, through which the coolantflows. The tubes of the single liner protective coverings are connectedin series from the outside to the inside in the path of flow of thecooling medium, and the space between the protective liner coverings isfilled with thermal insulation material. Streams of the reactor coolant,cooled down to temperatures as low as possible, are added again to themain gas stream after being heated, due to energy losses, before theentry into the reactor core. The cooling streams are fed into theexternal liner at a temperature of 0° C. The cooling necessary to reducethe temperature to this extent is produced in absorption plants (bymeans of waste heat of the total process). An auxiliary blower may beused to convey the coolant flowing through the liner at an increasedpressure at the reactor entry over that of the main gas stream. Thiscooling system has the advantage that no cooling water can enter thereactor cavity in the event of a leakage of the liner tubes (as a resultof an earthquake or other major disaster). Furthermore, the heat in theliner tubes, due to energy losses, is regained. Of course, additionalconstruction elements, such as absorption plants and auxiliary blowersare necessary to devices of this nature.

Finally, German Auslegeschrift No. 18 06 471 discloses an apparatus forcooling, by means of water, a cylindrical casing existing in aprestressed concrete vessel, which has a gas turbine assembly and heatexchangers arranged therein. The water streaming through tubes along thecasing wall is also the water which flows through the precooler and theintermediate cooler. The cooling of the hot gas line can be effected bya drawoff stream of the reactor cooling medium. The stream is drawn offfrom a point in the compressor of the turbine assembly. This drawoffstream is led through small annular chambers which are provided on theinternal surface of the hot gas line.

SUMMARY OF THE INVENTION

The present invention provides an improvement in high pressure-hightemperature gas turbine power plants having closed gas circuits whereinthe cooling of the reactor cavity and hot working gas transport conduitsare performed by cooling gas in the closed gas circuit.

An object of the invention is to equip the reactor pressure vessel of agas turbine power plant of the type described above with a hot sealingliner, and to improve the thermal isolation for the reactor pressurevessel and modifying it without increasing plant costs.

An advantage of the present invention is that a high temperature gasturbine power plant is provided with a reactor chamber that is cooledefficiently and safely with high pressure gas from the closed gascircuit.

These and other objects and advantages of the invention are attained ina preferred embodiment of the invention by cooling the inside surface ofa sealing liner in the reactor cavity, by means of a circuit gas of lowtemperature without additional external cooling, whereby the totalvolume of gas coming out of a high pressure compressor flows along theliner surface before its entry into recuperator units.

According to another embodiment of the invention, the circuit gas whichis preferably helium, directly enters the liner which has neither aninsulation nor a cooling system on its inside surface at temperaturesfrom 100 to 140° C. Since these temperatures are produced in the plantitself, additional construction elements or members such as absorptiondevices are not required.

In a further advantageous embodiment of the invention, the circuit gascoming from a high pressure compressor is led through a gas conduitrunning coaxially to the hot gas conduit leaving the nuclear reactor.The gas from the high pressure compressor is cooling gas, and flowsupwards in an annular chamber or free space between a thermal barrierand a sealing liner. The gas then leaves the free space through a secondgas line flowing to the recuperators and running coaxially to a gasconduit which carries heated gas into the nuclear reactor cavity.

According to the invention, a gas turbine power plant is providedcomprising a pressure vessel, a nuclear reactor as a heat source housedwithin a cavity in the pressure vessel, a gas turbine assembly housedwithin the pressure vessel having a gas turbine, means for compressingcircuit gas and means for recuperative heat exchange, a thermal barrierwithin the cavity in the pressure vessel and defining an areasurrounding the nuclear reactor, a sealing liner within the pressurevessel sealing the cavity, surrounding the thermal barrier and defininga free space between the thermal barrier and the sealing liner, andmeans for circulating cooling gas through the free space.

Furthermore, a method is disclosed for cooling a gas turbine power plantas described above comprising flowing the working gas of the power plantin a cool state through the free space located between the barrier andthe sealing liner thereafter flowing the gas from the free space intothe area defined by the thermal barrier and thereafter flowing the gasout of the area defined by the thermal barrier in its heated state intothe gas turbine.

In the gas turbine power plant of the present invention, the cooling gascirculation means advantageously comprises a cooling gas inlet conduitjoining a high pressure compressor and the free space, and a cooling gasoutlet conduit joining the free space and the recuperative heat exchangemeans. The high pressure compressor releases the total volume of itscooling gas into the free space, and after circulation in the freespace, the recuperative heat exchange means receives the total volume ofthe cooling gas.

In a preferred embodiment, the cooling gas inlet and outlet conduits areformed by coaxial conduit members, wherein the cooling gas circulates inthe outer conduit about the inner conduit containing heated gas.

The means for recuperative heat exchange is advantageously formed by acombination of a recuperator unit, a precooler unit, and an intermediatecooler unit connected in series generally to the aforementioned outletconduit. More than one group of recuperator, precooler and intermediatecooler units may be advantageously employed.

The means for compressing the circuit gas advantageously utilizes a highpressure compressor and a low pressure compressor. The compressors areindividually connected in series to the recuperator, precooler andintermediate cooler units described above.

The recuperative heat exchange means as described is connected, inaddition to the outlet conduit, also to the discharge conduit of the gasturbine. Accordingly, heated working gas leaving the gas turbine is ableto flow through the recuperator units, precooler units and intermediatecooler units countercurrently to the flow of the alreadly cooled gasalso flowing in the recuperator, precooler and intermedite cooler unitsfrom the outlet conduit. Accordingly, the coolest gas discharged fromthe high pressure compressor flows through the free space to cool thesealing liner and thereafter is heated in the recuperative heat exchangemeans by countercurrent flow with the heated gas discharged from theturbine, thereafter flowing into the area defined by the thermal barrieraround the nuclear reactor to be further heated to the high temperaturesnecessary for operation of the gas turbines.

The compressor units, the gas turbines, and the recuperator units,precooler units, and intermediate cooler units are all contained invertical recesses in the wall of the pressure vessel, and are connectedby conduits running through the pressure vessel contained similarly inconduit recesses in the walls of the pressure vessel. The conduitsjoining the various components of the gas turbine power plant areadvantageously coaxial conduits, wherein the gases of high temperaturesflow within the inner conduits, and the gases of cooler temperature flowin the outer conduits. The area defined by the thermal barrier isconnected to a heated gas inlet conduit and, a heated gas outlet conduitwhich advantageously are surrounded by the cooling gas flowing into andout of the free space formed by the thermal barrier and the sealingliner. Similarly, the gas turbine contains an inlet conduit and anoutlet conduit with the inlet conduit communicating directly with theheated gas outlet from the area defined by the thermal barrier, and theturbine outlet conduit being in direct communication with therecuperator units. Advantageously, the recuperative heat exchange meansand the gas compressor means may be arranged so that a recuperator unitis connected to a precooler unit and the precooler unit is in turnconnected to a low pressure compressor unit, which is connected to anintermediate cooler, which in turn is connected to a high pressurecompressor unit.

When employing a gas turbine power plant whose heat exchangers arearranged in vertical recesses in the wall of the reactor pressurevessel, the thermal isolation of the reactor pressure vessel canadditionally be advantageously increased in a further embodiment by alsofeeding the recuperator units with a gas stream of low temperature,whereby the high pressure gas is led into a chamber, usually an annularchamber, between the casing of the recuperators and the sealing linersof the recesses. This arrangement makes possible good cooling of thereactor pressure vessel in the region of the recuperator units.

In other embodiments of the invention, the liner of the reactor cavityis equipped on the outside of the liner, i.e. in the area of thepressure vessel wall, with a conventional thermal insulation and coolingsystem. A further improved thermal insulation of the reactor pressurevessel can be achieved by means of this additional feature. In order tosave on costs, it is not necessary that the entire liner of the reactorcavity be provided with an insulation and cooling system, but instead,that the thermal insulation system be attached only at those pointshaving highest temperatures.

In a preferred embodiment, the cooling system of the liner may beconnected to the main cooling system, i.e. it is in communication withthe secondary side of the precoolers, existing in the primary or gascircuit. The cooling water circuit may be designed such that it flows atfirst through the secondary side of the precoolers, with cooling gasflowing through on the primary side before it enters the cooling systemof the liner.

If the heat exchangers of the gas turbine power plant according to theinvention are installed in vertical recesses in the wall of the reactorpressure vessel, as mentioned above, it is advantageous to feed theprecoolers and intermediate coolers with water at the side of thecasing. The water is fed into an annular chamber between the casing ofthe precoolers and intermediate coolers. It is therefore advantageousfor the recesses in this instance, as well as in other embodiments, tocontain sealing liners, such as steel liners. This design also leads toa decrease of the temperature of the wall of the reactor pressure vesselin the area of the recesses.

The cooling system for the liner of the reactor cavity can be, but neednot be, connected to this cooling system.

The gas turbine power plant according to yet another embodiment of theinvention can be equipped with a conventional afterheat removal systemcomprising several coolers and blowers. In each case, one cooler and oneblower are installed above each other in a recess in the wall of thepressure vessel. During stand-by operation, the total afterheat removalsystem flows, preferably by a by-pass of cold high pressure gas, suchthat the cold gas stream is directed in each case from the bottom of therecesses between the sealing liner of the recesses and the casing ofeach cooler-blower unit upwards to the blowers after which if flowsthrough the coolers from the top to the bottom.

BRIEF DESCRIPTION OF THE DRAWINGS

The operation of the gas turbine power plant according to the inventionis schematically illustrated in the drawings. A single loop-plant withintermediate cooling and hot gas conduits is illustrated; the connectionof the heat exchangers is also advantageously designed with two circuitsbut for the sake of clarity, only one loop is shown as follows:

FIG. 1 shows a cross-sectional top view of the plant according to theinvention;

FIG. 2 shows a turbine power plant according to the invention;

FIG. 3 shows a cutout of the sealing liner of the reactor cavity withthermal insulation and a cooling system, and

FIG. 4 shows the cooling system of a precooler of a nuclear power plant.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1 and 2 illustrate a prestressed concrete vessel 1 cylindricallydesigned and arranged centrally inside a safety tank (not shown) made ofsteel reinforced concrete and having a cylindrical shape. Within theprestressed concrete vessel 1, there are arranged a high temperaturereactor 2 and the other components of the primary or cooling gascircuit, consisting of a turbine, a high pressure and a low pressurecompressor and heat exchangers. As will be further described below, theconnection of the heat exchangers are designed with two loops orcircuits, wherein a recuperator, a precooler and an intermediate coolerare contained in each circuit.

The high temperature reactor 2, installed in a cavity 3, is agraphite-modified, helium-cooled reactor, the fuel elements of which maybe ball or block shaped. A hot gas collection chamber 4 is located belowthe bottom of the reactor core for collecting the heated gas released bythe reactor core. A cold gas collection chamber 5 is provided above thereactor for collecting the gas flowing back from the main circuit beforeit is led back to the reactor core. The reactor core is surrounded by acylindrically designed thermal barrier 6, and the cavity 3 has a sealingliner 7 which is not equipped on its side facing the reactor 2 with anythermal protection means, such as isolation or cooling system forinsulating against the loss of heat. Between the thermal barrier 6 andthe liner 7, there is arranged an annular chamber 8. The hightemperature reactor 2 is connected to the remaining components of themain circuit by two outlet connecting ducts 9, attached to the hightemperature reactor 2 at the bottom by the same inlet connecting ducts10 attached on top. Vertically beneath the high temperature reactor 2,is arranged a horizontal duct 11 in the prestressed concrete vessel. Asingle shaft gas turbine 12, a low pressure compressor 13, and a highpressure compressor 14 are located within the vessel in separatehousings. The compressors are situated with the gas turbine on a commonshaft. A generator (not shown) which is arranged in the safety tank, iscoupled to the gas turbine 12. The gas turbine and the compressors havetwo oppositely, horizontally arranged connecting ducts for each gasline.

Two vertical gas ducts 15 extend adjacent the gas turbine 12 upwards tothe level of the bottom of the reactor core. A hot gas line 16 isinstalled in each of these gas ducts. Each hot gas line 16 is connectedto one of the reactor outlet connecting ducts 9 and with one of the twoturbine inlet connecting ducts. In the upper part of the prestressedconcrete vessel 1, there are two more vertical gas ducts 17, in anarrangement similar to that of vertical gas ducts 15. In each case, onecold gas line 18 is connected to one of the two reactor inlet connectingducts 10.

Six vertical pods 19 are arranged in a partial circle (see FIG. 1)around the reactor cavity 3, each pod being closed by explosion-prooflid 20. The pods 19 act to enclose the heat exchangers such that theyare arranged, as shown in FIG. 1, in symmetrical arrangement withrespect to the horizontal duct 11, two recuperators 21, two precoolers22, and two intermediate coolers 23. All of the heat exchangers areinstalled at the same level as the reactor cavity 3. Both recuperators21 are designed in box construction, and are operated countercurrently.The high pressure gas fed in from above is led through the interior oftubes 31 (see FIG. 2). The precoolers 22 and the intermediate coolers 23are also designed in box construction and are operated countercurrently.The water, flowing within the tubes, enters the coolers from below. Allof the heat exchangers are surrounded by a pressure casing 33, whichseparates the inlet and outlet streams.

At the same level as the horizontal duct 11, there are provided severalhorizontal gas lines in the prestressed concrete vessel for connectingthe heat exchangers of one loop or circuit with each other, or with thegas turbine assembly, respectively. As depicted in FIG. 1, a gas line 24runs between the recuperator, and the precooler of each loop, while theconnection between both recuperators 21, and the turbine outletconnecting duct, is effected in each case by a gas line 25. The gasflows in each case through a gas line 26 from the precoolers 22 to thetwo inlet connecting ducts of the low pressure compressor, and betweenthe low pressure compressor outlet and the two intermediate coolers 23,by virtue of a gas line 27 provided in each case. On a somewhat lowerplane, there are located two gas lines 28 (dashed lines in FIG. 1) whichconnect the two intermediate coolers 23 with the inlets of the highpressure compressor.

From the high pressure compressor 14, to the two recuperators 21, thegas is led through vertical gas ducts 15 and 17, over a large part ofits flow, whereby it flows along the outside of the hot gas lines 16 andthe cold gas lines 18, which are arranged as coaxial gas lines. On itsway from the gas duct 15 to the gas duct 17, the gas is led into thereactor cavity 3, coaxially to the reactor outlet connecting ducts 9,and enters the annular chamber 8 between the thermal barrier 6, and theliner 7. While it flows upwardly in this annular chamber, it cools theliner 7 which is equipped additionally with a means for insulatingagainst the loss of heat in the prestressed concrete vessel 1 (see FIG.3).

At the upper end of the vertical gas duct 17, there is provided, in eachcase, a horizontal connection line 29 of coaxial construction incommunication with one of the two pods 19 in which the recuperators 21are installed. Above the two recuperators, there is, in each case,arranged a gas distributor 30, serving also as a support through whichthe gas is distributed to the tubes 31. The upward feedback of the gasis effected in a central tube (not shown). The inner conduit 32 of thehorizontal connecting line 29 is in each case connected to one of thetwo cold gas lines 18.

All recesses in the prestressed concrete vessel 1 are coated with asealing skin or liner made of steel. In the region of the coaxial gaslines in the gas ducts 15 and 17 and the horizontal connecting lines 29,only small temperature loads occur at the sealing liners, since the hotor warm gas streams, respectively, are surrounded in each case by coldergas streams. Besides the six vertical pods for the heat exchangers,there are provided in the prestressed concrete vessel 1, three othervertical pods 34 which are arranged along a circle having a radiussmaller than that of the six vertical pods (dashed lines in FIG. 1).These act as an afterheat removal system, and, as shown in FIG. 3, aremade up of the conventional cooler 35 and blower 36. Each cooler 35 andblower 36 is installed one upon the other in one of the pods 34. Thecooler-blower units are each in communication with the high temperaturereactor 2 by means of a coaxially arranged gas line 37.

During stand-by operation, a by pass of cold, high pressure gas flowsthrough the cooler-blower units as shown by dotted arrows in FIG. 2. Thecold gas stream is led upwardly from the bottom of each pod 34 into anannular chamber between the sealing liner of the pod and the coolercasing. It then enters the blower and flows again through the cooler 35in a downward direction. During the operation of the afterheat removedsystem, the flow direction is reversed, whereby the entry of the gasinto the reactor core is effected through special borings in the top ofthe thermal barrier 6 (not shown).

The main or turbine circuit will now be described with reference toeither of the two identical heat exchanger loops connected in parallel.The pressure during operation ranges between about 72.9 and 22.9 bars,while the temperature ranges between an upper limit of about 850° C. anda lower limit of about 20° C. On the hot gas side, the gas flows at 850°C. and 70 bar directly from the hot gas collection chamber 4 through thecoaxial hot gas lines 16 to the two inlet flanges of the gas turbine 12.

In the gas turbine 12, the working gas is released at a pressure ofabout 24.14 bars, and enters the recuperator 21 at a temperature ofabout 502.5° C. through the gas lines 25 at the side of the recuperator21 and from the bottom. The gas is then streamed through the recuperator21 from the bottom to the top. As a result, it is cooled down to about147.7° C. by the cold gas flowing countercurrently at the high pressureside of the recuperator 21. Below the distributor 30, the gas stream isreversed 180°, and is led back between the casing of the recuperator 21and the sealing liner of the pod 19 to the bottom of the pod. The gasreaches the precooler 22 through the gas line 24 and flows from thebottom to top between the sealing liner of the pod and the casing of theprecooler 22. It enters the precooler after a reversal of the gas flowalong the side of the casing from the top to the bottom. Here, the gasis cooled down to the lowest process temperature of 20° C., before it isled to the inlet of the low pressure compressor 13 through the gas line26, after leaving the low pressure. The gas having a pressure of about41.2 bars is led to the intermediate cooler 23 through the gas line 27,flowing through it in the same manner as the precooler 22 and flowingout of it at a temperature of about 20° C.

The gas reaches the inlet of the high pressure compressor 14 through thegas line 28 in which its pressure is increased to the maximum processpressure of about 72.9 bars. At the outlet of the high pressurecompressor 14, the working gas behind the diffuser is deflected by 180°and flows around the entire gas turbine assembly. It then enters thevertical gas duct 15 through which it flows upwardly along the outsideof hot gas line 16. It is then led upwardly at a temperature of100°-140° C. through the annular chamber 8 into the reactor cavity 3,whereby it directly impinges the liner 7 at this temperature.

From the annular chamber 8, the cold, high pressure gas then flowsthrough the vertical gas duct 17, and the horizontal connecting line 29whereby it passes along the outside of the cold gas line 18 into therecuperators 21. In the recuperator 21, it is distributed among thesingle tubes 31 by the distributor 30. During the flowing through in thetubes 31 from the top to the bottom, the operation gas is heated by theturbine gas, flowing countercurrently along the side of the casing. Inthe central tube (not shown), it is then led upwardly and leaves therecuperator 21 through the inner conduit 32 of the coaxial horizontalconnecting line 29. Through the cold gas line 18, and the reactor inletconnecting duct 10, the gas finally reaches the cold gas collectionchamber 5 of the high temperature reactor 2.

FIG. 3 shows a section of the prestressed concrete vessel 1 with theliner 7, and its cooling system 38. This comprises a number of coolinglines, which are arranged in a thermal insulation layer 39 along theside of the concrete. The liner 7 is mounted along this layer by meansof anchorings 40. In the prestressed concrete vessel 1, there arearranged axially running bracing cables, as well as annular bracingcable 42 around the circumference of the vessel. Furthermore, in FIG. 3,there can be seen the thermal barrier 6 in the cavity 3, and the annularchamber 8.

FIG. 4 illustrates a precooler 43 in another embodiment of the nuclearpower plant with a cooling system which is connected to the coolingsystem 38 of the liner 7. This precooler is installed within a pod 19,situated in the prestressed concrete vessel 1. The feed of helium comingfrom the recuperator is effected from the top through the externalconduit 44 of a coaxial gas line. The gas is led off again out of theprecooler 43 through internal conduit 45 to a compressor, as indicatedby the arrows. The cooling water enters the precooler 43 from thebottom, and flows in the manner indicated by the black arrows. Afterpassing through the precooler 43, it is led along an annular chamber 46,which is bordered by the pressure casing 33 of the precooler and thesealing liners 47 of the pod 19 through the lines 48. The annularchamber 46 is in communication with the cooling system 38 of the liner 7through conduit 48, thus permitting the flow of cooling water betweenthe precooler and the liner cooling system.

The cooling system of a recuperator can also be designed in a similarfashion except, that instead of passing cooling water through theannular chamber between the pressure casing 33 of the recuperator andthe sealing liner 47 of the pod 19, low temperature helium from theprimary circuit (not shown) is flowed through the annular chamber.

The specification and drawings set forth preferred embodiments of theinvention. It should be noted, however, that the invention is notlimited to those specific embodiments and methods specificallydisclosed, but extends instead to all embodiments substitute andequivalent constructions falling within the scope of the invention, asdefined by the claims.

What is claimed is:
 1. A gas turbine power plant comprising:a pressurevessel; a nuclear reactor as a heat source housed within a cavity insaid pressure vessel; a gas turbine assembly housed within said pressurevessel having a gas turbine, means for compressing circuit gas and meansfor recuperative heat exchange; a thermal barrier within said cavity insaid pressure vessel and defining an area surrounding said nuclearreactor; a sealing liner within said pressure vessel sealing saidcavity, surrounding said thermal barrier and defining a free spacebetween said thermal barrier and the sealing liner; and means forcirculating cooking gas through said free space comprising a cooling gasinlet conduit joining said high pressure compressor and said free space,and a cooling gas outlet conduit joining said free space and saidrecuperative heat exchange means, said high pressure compressorreleasing the total volume of cooling gas to said free space and saidrecuperative heat exchange means receiving the total volume of coolinggas after circulation through said free space.
 2. The gas turbine powerplant as in claim 1, wherein each of said cooling gas inlet and outletconduits comprise the outer conduit of a coaxial conduit member forcirculation of cooling gas about an inner conduit member.
 3. The gasturbine power plant as in claim 2, wherein said means for recuperativeheat exchange comprises a recuperator unit, a precooler unit and anintermediate cooler unit connected in series to said outlet conduit. 4.The gas turbine power plant as in claim 3, wherein said means forcompressing circuit gas comprises a high pressure compressor and a lowpressure compressor, each individually connected in series with saidrecuperator, precooler and intermediate cooler units.
 5. The gas turbinepower plant as in claim 4, wherein said recuperative heat exchange meansis also connected to said gas turbine.
 6. The gas turbine power plant asin claim 5, wherein said units of the recuperative heat exchange means,said compressor and said gas turbine are contained in vertical recessesin the wall of said pressure vessel, and are connected by conduitscontained in conduit recesses in the walls of said pressure vessel. 7.The gas turbine power plant as in claim 6, wherein the interior of saidthermal barrier is in communication with heated circulating gas ofhigher temperature than said cooling gas.
 8. The gas turbine power plantas in claim 7, wherein the area defined by the thermal barrier isconnected to a heated-gas inlet conduit and heated-gas outlet conduit,and said heated circulating gas further absorbs heat energy from saidnuclear reactor within said thermal barrier.
 9. The gas turbine powerplant as in claim 8, wherein each of said heated-gas inlet and outletconduits comprise the inner conduit of said coaxial conduit memberwhereby each heated-gas inlet and outlet conduit is surrounded by one ofsaid cooling gas conduits.
 10. The gas turbine power plant as in claim9, wherein said heated-gas inlet conduit is connected to saidrecuperative heat exchange means.
 11. The gas turbine power plant as inclaim 9, wherein said heated-gas outlet conduit is connected to said gasturbine.
 12. The gas turbine power plant as in claim 4, wherein said gasturbine comprises a turbine inlet conduit and a turbine outlet conduit,and said turbine outlet conduit is connected to said recuperator unitfor removing heat from gases leaving the outlet conduit of the turbine.13. The gas turbine power plant as in claim 12, wherein said recuperatorunit is connected to said precooler unit having a precooler inlet and aprecooler outlet and, wherein said precooler outlet is connected to theinlet of said low pressure compressor unit, and wherein said lowpressure compressor unit has an outlet which is connected to the inletof said intermediate cooler unit having an inlet and outlet, said outletof said intermediate cooler unit being connected to the inlet of saidhigh pressure compressor unit having an inlet and an outlet, and saidoutlet of said high pressure compressor unit is connected to saidcooling gas inlet conduit of said free space.
 14. The gas turbine powerplant as in claim 13, further comprising a thermal insulation layerbetween said sealing liner and the cavity forming wall of the pressurevessel; a passageway for cooling fluid disposed in said insulationlayer; and means for circulating cooling fluid through said coolingpassageway.
 15. The gas turbine power plant as in claim 14, furthercomprising means for circulating cooling fluid through said precooler,intermediate cooler, and recuperator units.
 16. The gas turbine powerplant as in claim 15, wherein said cooling fluid in said coolingpassageway, precooler and intermediate cooler units is water and saidcooling fluid in said recuperator unit is said cooling gas.
 17. The gasturbine power plant as in claim 15, wherein the means for circulatingcooling fluid comprises a cooling fluid inlet for each of saidprecoolers, intermediate cooler and recuperator units, a chambersurrounding each of said precooler, intermediate cooler and recuperatorunits, a cooling fluid outlet for each of said chambers and a coolingfluid circulation source; whereby cooling fluid enters said coolingfluid inlets, flows through said units into said chambers, through saidoutlets and back to said cooling fluid circulation source.
 18. The gasturbine power plant as in claim 4, further comprising an afterheatremoval system comprising at least one blower and corresponding coolerunit located within recesses provided in the walls of said reactorpressure vessel and communicates with said cavity in said pressurevessel.
 19. A method for cooling the gas turbine power plant of claim 1comprising:flowing the working gas of the power plant in a cool statethrough said free space located between said barrier and said sealingliner thereafter flowing said gas from said free space into the areadefined by said thermal barrier and thereafter flowing said gas out ofthe area defined by said thermal barrier in its heated state into saidgas turbine.
 20. The method as defined by claim 19, wherein said gasflows from said free space into said recuperator heat exchange meansprior to flowing within the area defined by said thermal barrier. 21.The method as defined by claim 20, wherein said gas flows from said gasturbine into recuperative heat exchange means countercurrently to saidgas entering said recuperative heat exchange means from said free space.22. The method as defined by claim 21, wherein said gas flows in aclosed gas circuit comprising said free space, said recuperative heatexchange means, said compressor means, said area defined by said thermalbarrier and said gas turbine.